# required-string-property-missing-min-length

Requires that every required property in the API definition with type `string` has a `minLength`. 

|OAS|Compatibility|
|---|---|
|2.0|✅|
|3.0|✅|
|3.1|✅|

## API design principles

The `minLength` keyword constrains string values. When a property of type `string` is `required`, defining the `minLength` helps prevent common mistakes, such as empty strings. Use the `minLength` property as a best practice to ensure data integrity and enhances the overall quality of the API.

## Configuration

To configure the rule, add it to the `rules` object in your configuration file.
Set the desired [severity](/docs/cli/rules.md#severity-settings) for the rule.

```yaml
rules:
  required-string-property-missing-min-length:
    severity: error
```

## Configuration


|Option|Type|Description|
|---|---|---|
|severity|string|Possible values: `off`, `warn`, `error`. Default `off` (in `recommended` configuration). |

An example configuration:

```yaml
rules:
  required-string-property-missing-min-length: error
```

## Examples


Given this configuration:

```yaml
rules:
  required-string-property-missing-min-length: error
```

Example of an **incorrect** schema:

```yaml Bad example
schemas:
  User:
    type: object
    required:
        - name 
    properties:
      name:
        description: User name
        type: string
        
```

Example of a **correct** schema:


```yaml Good example
schemas:
  User:
    type: object
    required:
        - name 
    properties:
      name:
        description: User name
        type: string
        minLength: 2
```

## Related rules

- [no-invalid-schema-examples](./no-invalid-schema-examples.md)
- [response-contains-property](./response-contains-property.md)
- [Custom rules](./custom-rules.md)

## Resources

- [Rule source](https://github.com/Redocly/redocly-cli/blob/main/packages/core/src/rules/common/required-string-property-missing-min-length.ts)
- [Schema docs](https://redocly.com/docs/openapi-visual-reference/schemas/)